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Ewing's sarcoma
Image:EwingSarcomaTibia.jpg Ewing's sarcoma is the common name for primitive neuroectodermal tumor. It is a rare disease in which cancercells are found in the boneor in soft tissue. The most common areas in which it occurs are the pelvis, the femur, the humerus, and the ribs. James Ewing(1866-1943) first described the tumor, establishing that the disease was separate from lymphomaand other types of cancer known at that time. Ewing's sarcoma occurs most frequently in male teenagers. Ewing's sarcoma is the result of a translocation between chromosomes 11 and 22, which fuses the EWS gene of chromosome 22 to the FLI1 gene of chromosome 11.
Clinical FindingsEwing's sarcoma is more common in males and usually presents in childhood or early adulthood, with a peak between 10 and 20 years of age. It can occur anywhere in the body, but most commonly in the pelvisand proximal long tubular bones. The metaphysis and diaphysis of the femurare the most common sites, followed by the tibiaand the humerus. Thirty percent are overtly metastaticat presentation. The most common clinical findings are pain and swelling. Imaging FindingsOn conventional radiographs, the most common osseous presentation is a permeative lytic lesion with periostealreaction. The classic description of lamellated or "onion skin" type periostealreaction is often associated with this lesion. Plain films add valuable information in the initial evaluation or screening. The wide zone of transition (e.g. permeative) is the most useful plain film characteristic in differention of benign versus aggressive or malignant lytic lesions. MRIshould be routinely used in the work-up of malignant tumors. MRIwill show the full bony and soft tissue extent and relate the tumor to other nearby anatomic structures (e.g. vessels). Gadoliniumcontrast is not necessary as it does not give additional information over noncontrast studies, though some current researchers argue that dynamic, contrast enhanced MRI may help determine the amount of necrosis within the tumor, thus help in determining response to treatment prior to surgery. CTcan also be used to define the extraosseous extent of the tumor, especially in the skull, spine, ribs and pelvis. Both CTand MRIcan be used to follow response to radiation and/or chemotherapy. Bone scintigraphycan also be used to follow tumor response to therapy. Differential DiagnosisOther entities that may have a similar radiologic presentation include osteomyelitis, osteosarcoma(especially telangiectatic osteosarcoma) and eosinophilic granuloma. Soft tissue neoplasms such as malignant fibrous histiocytoma that erode into adjacent bone may also have a similar appearance. TreatmentBecause almost all patients with apparently localized disease at diagnosis have occult metastatic disease, multidrug chemotherapyas well as local disease control with surgery and/or radiation is indicated in the treatment of all patients (2). Treatment often consists of adjuvant chemotherapygenerally followed by wide or radical excision, and may also include radiotherapy. Complete excision at the time of biopsy may be performed if malignancy is confirmed at that time. PrognosisStaging attempts to distinguish patients with localized from those with metastaticdisease. Most commonly, metastasesoccur in the chest, bone and/or bone marrow. Less common sites include the central nervous systemand lymph nodes. Survival for localized disease is 65-70% when treated with chemotherapy. Survival for metastaticdisease is 25-30%. Useful LinksNational Cancer Institute listing for Ewing's sarcomade:Ewing-Sarkom fr:Sarcome d'Ewing
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